Since you can tell if a part was applied at the factory by the black finish on the frame parts, I looked to see what was under the helper spring stops on the 43 Chevvy.
Since I had already started sandblasting, one side was already wiped clean.. but I did find this on the passenger side:
So that leads me to believe that the helper springs were factory installed (its kinda hard to tell, but the black frame finish is in the pits). Compare that with what was under the steering box hold down brackets:
And you see the same finish. So it appears that they were a factory part.